It's not really a long run until probably 90 minutes. I can't find the article I wanted to link on this, but to edify Trent some I'll at least link this one ﻿﻿http://runningtimes.com/Article.aspx?ArticleID=21172&PageNum=3 where Magill mentions growth hormone diminishing after 75 minutes. I once saw a great article outlining how the body produces ideal growth hormone during 30-45 minutes of running, still does okay from 60-75 minutes, and then after that you start getting to the point where going further is a calculated risk. The crux was that going at least 90 minutes for a true long run is probably good, but over 2 hours begins to be more risk than reward.

There was a study conducted (usking some kind of EKG?) within the last year on ultra runners that showed they didn't take any permanent damage by running for hours on end, but combining this with other information like what I previously said will show you that it's really easy for a runner to get into that gray area where it's anyone's guess whether the run is actually helping or hurting them overall. My empirical experience for myself and what I've seen is that 90 minutes is a little low and 150 minutes is a little high, so 2 hours is a pretty good deal.

For an elite marathoner, that's going to mean 20ish miles if the aim for the middle ground, as much the whole marathon distance if they aim higher, and maybe just 18 miles if they aim a little lower. For slower runners, this means a much reduced volume total. When a runner reads that professionals are doing 20 milers, duration is closer to what's applicable than mileage and even still that is somewhat inprecise. But let's say pros do 20 miles in 2 hours. That means a person running a 10:00 pace should probably go 120 minutes and not over 150 minutes and get maybe 12 to 15 miles. That's what is still within the range of being HEALTHY for this individual's long run.

Then this runner wants to do the marathon. Running the marathon isn't healthy for these individuals (which I'd argue makes the achievement quite a bit more extraordinary when they do it). What I mean by this is that during that run obviously the risk of damage far exceeds the reward from the run. This is the case for most marathoners, but especially for non-professionals. And the problem is that the non-professionals try too often to do 4 hour long runs in their preparation when this only puts them in the risk zone much more than the reward zone for getting a positive physical adaptation from the run. This is why the Hansons will tell most runners to do 16 or 18 mile long runs (per their public training plan) and why Daniels on in a Flotrack interview said average runners should stay below race distance.

-Distance considerations.

Calorie burn is more directly related to distance and if you consider things in terms of glycogen and fat depletion and the consequential adaptations the body makes, then runs that approach "the wall" may provide a training impetus. For a generic athlete that might be around 18 miles, but for some it will be less and others it will be more depending on usage efficiency and other factors.

-Conclusion.

In decently trained athletes, the ideal duration in the risk/reward debate coincides with the duration the athlete needs to run to hit the correct distances to also impact their fueling adaptations. So 16-24 mile long runs become the norm for a lot of people depending on what kind of shape the individual is in.

The ideal distance is highly individual and in my opinion the cited Galloway figure is sadly too high for the runners willing to consider Galloway a trustworthy reference.

I think that training for a HM should be about the same a training for a Full marathon; with just a little less focus on long runs with a little more focus on tuning up with intervals, 5K and 10k races.

CanadianMeg I think you would benefit from at least one run in the 2.5 to 3 hour range (Don't worry if you don't hit 16). Not very often, but once and a while with plenty of time to recover before your next race (4-8 weeks). Keep up good work with the 10-11 mile runs those will do wonders to improve your fitness.

Even deep in marathon training, I'm going to be very reluctant (or cautious) to get over 3 hours on a long run. The recovery time means the next week's first 3 - 4 days of training have no quality. For me.

oh - is that what happened to me this week?! I recently started running a recovery pace 3-miler the day after my long run. I don't know if it's that addition or the 14er on Saturday or last Wednesday's bump up in my tempo run pace, but Monday and Tuesday (that would be today) - OUCH! Saturday didn't take me 3 hours, so maybe it's the next-day run - may be not good for me. I'm really not sure, but my legs are unhappy. Tomorrow nights tempo-8 is out the window. Better to be safe and run another slow 5 than risk overdoing it.